This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 Excerpt: ...its description till the last. The St. Agnes elvan averages 15 feet in width and is first seen in the cliffs near St. Agnes Head. It is possible to land from a boat and examine the rock, which is washed by the sea at high tide. It is a fine quartz-porphyry of the ordinary type. At the top of the cliff the elvan has the ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 Excerpt: ...its description till the last. The St. Agnes elvan averages 15 feet in width and is first seen in the cliffs near St. Agnes Head. It is possible to land from a boat and examine the rock, which is washed by the sea at high tide. It is a fine quartz-porphyry of the ordinary type. At the top of the cliff the elvan has the same character, but is remarkable y for enclosing a large fragment of greisen, similar to that in the St. Agnes granite mass, and. doubtTBss, caught up as the elvan made its way to the surface. This shows that the date of intrusion was posterior to that of the alteration of the granite to greisen.. The dyke can be traced across the open land to a bjg qiiarjy on the edge of the cliff north of the Beacon. In this exposure it presents quite a different character from that observed south of the Head. The mass of the rock is very fine-grained, tough, in colour a dull grey, with abundant tourmaline in small rosettes. In it small blebs of quartz are not uncommon, but never reach any size; and scattered irregularly throughout the mass are nests of felspar phenocrysts, the individual crystals reaching as much as two-thirds of an inch in length. The exposure here is as good as could be desired; yet there did not seem to be any definite arrangement of those nests with regard to the centre or periphery of the dyke. The tourmaline is mostly blue, and appears to be an original constituent of the rock. The felspar crystals throughout this exposure are completely kaolinized; and in the centre of the dyke is a seam of the rock which has been similarly affected in toto, ground mass and phenocrysts. Owing to the peculiar disposition of the felspar crystals in this quarry it is impossible to distinguish a " chilled margin." From this quarry the elvan s...
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PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
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PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
